The article “Ordered subsets algorithms for transmission tomography” by H. Erdogan and J. A. Fessler, Physics in Medicine and Biology, 44(11), November 1999 discloses an iterative reconstructing method for iteratively reconstructing an image from detection values acquired by using a computed tomography system. In an iteration step a forward projection through an actual image is performed for generating simulated detection values, a difference between the simulated detection values and the acquired detection values is determined, and updates are calculated from the difference using a noise model, which are then back projected for updating the actual image. Several of these iteration steps are performed, until a termination condition is fulfilled. Although the updates are calculated by using a noise model, the quality of the reconstructed image is still reduced.